The present embodiments relate to extracting carbonaceous substances from oil sand.
Large portions of the worldwide oil reserves exist in the form of oil sand. A mixture of rock, clay, sand, water, and bitumen or other heavy oils is understood by oil sand. Only bitumen, which typically exists with a viscosity of API 5° to 15° with respect to deposits, is mentioned in the following text as being representative for heavy oils, extra-heavy oils, or generally long-chain hydrocarbons. By corresponding process acts, the bitumen may be converted into synthetic crude oil.
Oil sand deposits, if the oil sand deposits lie in strata of shallow depth, are mined by, for example, open-cast mining. Oil sand deposits, however, often lie in deeper strata that are not accessible to open-cast mining or the mining of which would be uneconomical in open-cast mining. Oil sand deposits are typically mined after depths of about 60 m by in-situ processes since with these processes the removal of the surface layer, which lies above the oil sand deposit, is not necessary.
The common in-situ process is the steam assisted gravity drainage (SAGD). With the SAGD process, the bitumen, which is present in the earth in a deposit, is heated by superheated steam. As a result of the heat effect, the long-chain hydrocarbons of the highly viscous bitumen are broken down. The heating of the oil sand leads to a reduction of the viscosity of the bitumen that, as a result, becomes free-flowing and may be pumped out of the deposit in a conventional manner.
The device for the SAGD process includes at least one injection pipeline for feeding the superheated steam into the deposit and a production pipeline through which the fluid bitumen may be transported out of the deposit to the earth's surface. The injection pipeline and the production pipeline are laid inside the deposit essentially parallel to each other and extending horizontally one above the other. The injection pipeline and the production pipeline may have a distance of about 5 m to 10 m from each other in the vertical direction. In the horizontal direction, the pipes extend inside the deposit by a length of between several hundred meters and a few kilometers. The injection pipeline may be located above the production pipeline. As a result of the heating of the bitumen and the reduction of the viscosity thereof, the bitumen flows to the bottom downward on account of gravitational force and therefore towards the production pipeline and may be simply pumped out there and transported to the earth's surface. The transporting may be achieved either by oil lift pumps or by introduction of an overpressure in the deposit. The introduction of overpressure has the significant disadvantage, however, that earth displacements on the earth's surface (e.g., blow out) may occur in the surrounding area of the deposit, especially when the stratum above the deposit is of small thickness. For this reason, the steam pressure, before introduction into the deposit, may be reduced by a restrictor or a throttle valve to a pressure that is lower than the rock pressure in the region of the deposit. The throttle valve is arranged between the steam generator and the injection pipeline in this case. Since the steam pressure is reduced in the throttle valve, without being utilized, the process is inefficient.
For this reason, in German patent application 10 2012 000092.8, with the title “Device and method for extracting carbonaceous substances from oil sands,” it is proposed to arrange at least one steam turbine between the steam generator and the injection pipeline. By arranging the steam turbines between the steam generator and the injection pipeline, the pressure reduction, which is usually carried out via the throttle valve, without being utilized, may be utilized for power recovery. To this end, the steam turbine may be connected to a generator for power generation.
A further common in-situ process is electromagnetic gravity drainage (EMGD). With the EMGD process, the heating of the deposit is carried out using an electric/electromagnetic heating method, in which, for example, an inductive heating is carried out. The EMGD process is disclosed in the German patent application 10 2007 040605.5, with the title “Device for the in-situ transporting of bitumen or heavy oil,”. The EMGD process is also associated with large expenditure of energy.